SANFORD, Fla. —The jury hearing George Zimmerman's second-degree murder trial will not hear from a state voice expert who says Trayvon Martin screamed "stop" before being shot, a judge ruled Saturday.

Circuit Judge Debra Nelson's ruling prevents two state experts from testifying. The experts say a voice heard screaming in the background of a 911 call just before the shooting belonged to Trayvon, 17.

"There is no evidence to establish that their scientific techniques have been tested and found reliable," Nelson wrote in a 12-page ruling.

The judge, siding with defense experts, said that the methods applied by the state experts are not "widely accepted at this time" and are "new and novel."

Even so, the actual 911 call can be played in court and witnesses familiar with the voices of Zimmerman and Trayvon can testify to who they believe is screaming, the judge ruled.

The weekend decision is a big win for Zimmerman's lawyers, defense attorneys say.

"Certainly, the 911 call is coming in," said Mark O'Mara, an attorney for Zimmerman, Saturday. "What we need to do is play it and let the jury make a decision."

Zimmerman has pleaded not guilty to second-degree murder. The former neighborhood watch volunteer says he shot Trayvon in self-defense after being attacked. Prosecutors say he profiled and murdered Trayvon.

Opening statements in the trial start Monday. Six women will serve as jurors; two women and two men are alternates.

O'Mara said he would have liked to have found someone who could testify that it was Zimmerman screaming for help but evaluating the call was impossible.

Now, the jury will have to weigh the evidence presented in court and use the screams in context, O'Mara said.

Benjamin Crump, an attorney for Trayvon's family, said the facts of the case will be enough to get Zimmerman convicted.

"The evidence is overwhelming that George Zimmerman murdered Trayvon Martin," he said Saturday. "Unfortunately, Trayvon Martin isn't here to tell us his version."

Trayvon's mother has said that she believes her son was screaming on the call. Zimmerman says he was the one yelling.

A spokeswoman for the state attorney's office did not immediately return an e-mail and phone call seeking comment.

One of the prosecution's most influential witnesses may have been be Alan Reich, a voice-identification expert who says Trayvon is heard screaming "stop" in the background of a 911 call placed by a resident. The screaming stops abruptly when a gunshot is heard.

Nelson ruled Reich and Tom Owen, another expert for the prosecution, "testified in support of the own technologies and techniques."

"They have an interest in the outcome of this issue because it is their methodologies being tested," the judge said.

Nelson's ruling notes that Owen testified that he had marketed and had financial stake in software program he used to evaluate the 911 call, all reason to exclude him from testifying.

"It is clearly a win for the defense, because now there is nobody that's independent to contradict Zimmerman's account," said Randy Reep, a criminal defense attorney in Jacksonville.

However, Reep added that he believes Zimmerman now has to testify to convince a jury that he was screaming for his life.

Elizabeth Parker, a former prosecutor who is now a criminal defense attorney in Palm Beach, Fla., agreed with Nelson's decision. "The judge's ruling was absolutely correct," she said, explaining that the opinion of Owen and Reich were "too speculative" and would have confused the jury.

Had the experts testified Zimmerman would have had a solid ground for an appeal and would likely have been granted a new trial, Parker said.

Still, she thinks the ruling doesn't hurt the foundation of the state's case. "They didn't have this evidence when they made the arrest and filed charges," Parker said. "It's not anything that is going to prevent them from proceeding."

In a Frye hearing held over more than four days, prosecutors tried to convince Nelson that experts should explain their theories and let the jury decide. Defense attorneys brought their own experts — including a senior FBI official — who said it was impossible to identify the voice heard screaming for seconds.

Assistant State Attorney Richard Mantei argued Thursday to keep the prosecution's experts. "Let them (the jury) decide," he said, adding that Florida law favors allowing jurors to determine what to believe when issues are contested.

Don West, one of Zimmerman's attorneys, had argued that prosecutors' experts were using questionable scientific methods. He claimed that defense attorneys can't find anyone else who can hear what Reich says he hears.

"He's making it up," West said, claiming that there's no method anywhere in the world that can reliably test the seconds-long screaming from the 911 recording.

He added that trying to determine whose voice is on the call is a "waste of time."

Hirotaka Nakasone, an FBI official called by the defense, said the recording was too short and didn't meet the standards needed to be evaluated. Another defense expert said a voice that is screaming can't be identified no matter how long the recording.

James Wayman, a defense forensic voice expert, said Reich's report was bewildering, and methods used by Owen have never been used to evaluate recordings like the 911 call.

"A lot of this appears to be like magic," Wayman said. "I was baffled."